These effects are even greater when other drugs are mixed with marijuana. A user may also experience dry mouth and throat.

Q. What are its long-term effects?

A. Marijuana smoke contains some of the same cancer-causing compounds as tobacco, sometimes in higher concentrations. Studies show that someone who smokes five joints per week may be taking in as many cancer-causing chemicals as someone who smokes a full pack of cigarettes every day.

According to federal officials, the marijuana being taken by youngsters today is nearly twice as potent as it was in the 1980s. “There is no question marijuana can be addictive; that argument is over,” said Dr. Nora Volkow, director of the National Institute on Drug Abuse. “The most important thing right now is to understand the vulnerability of young, developing brains to these increased concentrations of cannabis.” This more potent marijuana increases physical and mental effects and the possibility of health problems for the user.

When young people start using marijuana regularly, they often lose interest and are not motivated to do their schoolwork. The effects of marijuana can interfere with learning by impairing thinking, reading comprehension, and verbal and mathematical skills. Research shows that students do not remember what they have learned when they are “high.”